Apparatus for feeding sheets

ABSTRACT

A sheet feeding apparatus includes an adjustable backstop assembly for supporting the trailing edges of a stack of sheets at varying heights above a feeding surface depending on the length of the sheets being fed. The backstop assembly is raised to a relatively high position above the feeding surface to permit the feeding of the bottom sheet of the stack by a conventional reciprocating spring feeder assembly when a stack of longer sheets is being processed, and adjusted to a relatively lower position to permit the feeding of the bottom sheet from a stack of shorter sheets by a new low-profile spring feeder assembly.

United States Patent Kuehn 51 Apr. 25, 1972 [54] APPARATUS FOR FEEDINGSHEETS 1 [72] Inventor: Frederick Reinhold Kuehn, Baltimore, tE'Yamlverjoseph wegbren M Asszstant Exammer-Bruce H. Sto ner, Jr.Attorney-Boyce C. Dent, Oscar B. Brumback and Olin E. [73] Assignee:Koppers Company, Inc. Williams 7 [22] Filed Apr 1 1970 ABSTRACT 21 l. N29 463 1 App 0 A 'sheet feeding apparatus includes an adjustablebackstop assembly for supporting the trailing edges of a stack of sheetsat 1.8. CI- 1 R, varying heights above a feeding surface depending onthe [51] Cl 3/24 length of the sheets being fed. The backstop assemblyis raised [58] Field Of Search ..4....27 H44, 4 l 35, 32 to a relativelyhigh position above the feeding surface to pen mit the feeding of thebottom sheet of the stack by a conven- [56] References cued tionalreciprocating spring feeder assembly when a stack of UNITED STATESPATENTS longer sheets is being processed, and adjusted to a relatively Ilower position to permit the feeding of the bottom sheet from Shields ata k of horter heets a new ]ow profi]e pring feeder as. 1,637,833 8/1927Mueller ...271/4l Semb|y 2,974,950 3/1961 Pasquinelli et al ...27l/443,409,289 1 H1968 Barnes ..271/44 7 Claims, 4 Drawing Figures DL iflUPPER pas/mm 20 LflWER 1 05/ T/ON BACKGROUND OF THE INVENTION 1. Fieldof the Invention This invention relates generally to sheet feeding andmore particularly to separators of the reciprocating bottom feeder type.

2. Description of the Prior Art Conventionally, an apparatus used tofeed sheets such as corrugated paperboard sheets from the bottom of astack comprises a backstop assembly for supporting the trailing edges ofthe sheets in a position which permits a standard feeder bar toreciprocate beneath the stack. The backstop assembly usually includesindividual backstops spaced laterally along a backstop support bar; thefeeder bar usually includes resilient spring feeder plates spacedlaterally along the bar and adapted to engage the trailing edge of thebottom sheet of the stack even though the trailing edge may be warped.

Palamenti U.S. Pat. No. 3,264,386 and Barnes U.S. Pat. No. 3,409,289show the use of a backstop in cooperation with a spring feeder assemblyfor feeding sheets into adjacent machinery for operations on the sheetssuch as printing, slotting, scoring, and the like. The trailing edge ofthe bottom sheet of a stack of long sheets rests ona support-ledgeprovided on each backstop to maintain the trailing edge of the stackabove the leading edge of the stack which rests on a feeding surface.The result is that the stack of sheets rests in a slightly inclinedposition. By long sheets is meant for example sheets longer than 22inches. The standard feeder bar rapidly reciprocates beneath the stackand feeds the sheets, one by one, from the bottom of the stack into theadjacent processing machinery.

When short sheets are fed by the standard bar in the prior art apparatusa problem arises. By short sheets is meant for example sheets about 10.5to 22 inches long, depending on the proportions of the machine. In theprior art apparatus the backstop is moved forward to support thetrailing edge of the stack. .This movement causes the angle of inclineof the stack to be increased. As a result, the standard feeder bar isoperating closer to the vertex of the angle formed by the inclined stackwith the feeding surface since the stroke of the feeder bar is fixed at,for example, about 10.5 inches. The standard feeder bar reciprocates tofeed the bottom sheet in the same manner regardless of sheet length.However the resilient action of the spring feeder plates changes withsheet length. The spring feeders are subject to more weight with thelarger sheets than with the smaller sheets. Consequently, the standardspring plates lift the stack of small sheets during the back stroke ofthe bar causing the stack to rapidly rock up and down as the barreciprocates.

In the past, to reduce the problem of rocking the stack of short sheets,a flat feeder bar i.e. one not having a resilient or flexible feederplate, was supposed to allow the short sheets to be fed without causingthe stack to rock. However this substitute required the replacing of thestandard backstop with a backstop not having a ledge for supporting thetrailing edge of the bottom sheet thereby letting the stack rest flatlywith respect to the feeding surface except for the thickness of the flatfeeder bar. A shortcoming of this arrangement, however, was the factthat the sheets were often warped and the flat feeder bar could notefficiently handle warped sheets since the flat feeder bar did notinclude resilient feeder plates independently operable to follow thecontour of the trailing edge of the sheet. Since the sheets arefrequently warped, the bar frequently failed to engage the trailing edgeof the bottom sheet or, worse yet, partially engaged the trailing edgethereby skewing the sheet and this usually resulted in jam-ups.

The present invention takes advantage of the superior feedingcharacteristics of the standard spring feeder bar for feeding longsheets but also provides improved feeding apparatus easily adjustablefor feeding either long or short sheets and adapted to take advantage ofthe superior characteristics of spring feeder plates in both instances.

SUMMARY or THE INVENTION The present invention contemplates the methodof feeding a stack of blanks by supporting the trailing edge of thestack with an adjustable backstop assembly and reciprocating a springfeeder bar between the stack and feeding surface with the improved stepof placing the backstop assembly at a first height above the feedingsurface for feeding long sheets and thereafter adjusting the backstop toa lower position above the feeding surface for feeding shorter sheets.

The foregoing method may be performed by a sheet feeding apparatus whichincludes adjustable backstops slidably mounted on wcdges secured to abackstop support bar for providing upper and lower positions above afeeding surface for supporting the trailing edges of both long and shortsheets, and a novel low-profile feeder bar having spring feeder platesof substantially increased resilience or flexibility placed laterallyalong the feeder bar.

The new backstop, when in the upper position, may be used to supportlong sheets in cooperation with a conventional spring feeder bar, or itmay be adjusted to the lower position and moved forward to support astack of short sheets. When the backstop is supporting short sheets, thenovel low-profile spring feeder bar is preferably used to feed the shortsheets from the bottom of the stack without rocking the stack as theconventional spring feeder tends to do. Adjusting the backstops to thelower position results in a greater distance between the warped sheetdeflector and the backstop support bar which permits the feeder bar toreciprocate through its normal cycle without striking a warped sheetdeflector, which is usually provided on the support surface forsupporting the leading edge of the stack, on the forward stroke orwithout striking the backstop support bar on the backstroke.

The above and further objects and novel features will appear more fullyfrom the following detailed description when the same is read inconnection with the accompanying drawings. It is to be expresslyunderstood, however, that the drawings are not intended as a definitionof the invention but are for the purpose of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation in partialcross-section illustrating the backstop and feeder bar assemblies of thepresent invention;

FIG. 2 is an enlarged side view in cross-section illustrating theadjustable mounting of a conventional spring feeder bar assembly in afeeder surface;

FIG. 3 is an enlarged side view of the low-profile spring feeder barassembly showing its configuration and height in comparison to theconventional spring feeder bar assembly of FIG. 2; and

FIG. 4 is an isometric view of part of the backstop assembly and thefeeder bar assembly of the present invention illustrating the lowerposition of the backstop in phantom outline.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the newsheet feeding apparatus is generally designated 10. Feeding surface 12supports a backstop assembly generally designated 20 and feeder barassembly 30. Trailing edge 42 of stack 40 is supported by backstops 22above feeding surface 12, and leading edge 44 of stack 40 is restrainedagainst forward movement by gate 50. Backstops 22 and gate 50 define ahopper for receiving the stack 40. The trailing edge 43 of bottom sheet46 rests on ledge support 23 and leading edge 45 of bottom sheet 46rests on warped sheet deflector bar 60. Feeder bar assembly 30 rapidlyreciprocates along the top of feeding surface 12 and engages thetrailing edge of each successive bottom sheet of stack 40 thus feedingsheets, one by one, from the underside of stack 40 through an opening 52beneath gate 50 to adjacent processing machinery (not shown).

Feeding surface 12 is the supporting base for sheet feeding apparatus10. Backstop assembly 20 is movably mounted on feeding surface 12 andmay be moved toward or away from I gate 50 depending on the length ofthe sheets being fed.

Feeder assembly 30 is provided to rapidly reciprocate between feedingsurface 12 and stack 40. To accomplish this, feeder bar assembly 30 isslidably mounted on slides 38 provided in feeding surface 12 as bestshown in FIG. 1.

Conventional feeder bar assembly 30a, FIG. 2, is efficient for feedinglong sheets and comprises spring feeder plates 32a including a lipportion 34a for engaging the trailing edge of bottom sheet 46 of stack40 at the completion of the backstroke. Thus, if long sheets are beingfed, feeder assembly 30a could be used in the same manner in whichfeeder assembly 30 is used in FIG. 1. When feeder bar assembly 30 movesforward toward gate 50, bottom sheet 46 is moved forward. In order forlip portion 34, FIG. 3, to engage the trailing edge of bottom sheet 46it is necessary that spring feeder plate 32 exert an upward force on theunderside of stack 40. Thus, spring 32 should not reach its freeposition while it is beneath stack 40 if it is to effectively engage thetrailing edges of each successive bottom sheet.

Conventional spring feeder plates 32a are stiff and therefore require asubstantial force to cause them to flex or bend. The weight of a stackof long sheets is great enough to overcome the upwardly directed forceexerted on the underside of the stack and the reciprocating feeder barassembly 30a does not cause stack 40 to rock or bounce as a result ofthe upward force of spring 32a. However, when a stack of short sheets isfed by the conventional feeder bar assembly 30a the substantiallylighter weight of the stack of short sheets is not sufficient towithstand the upward force exerted by spring feeder plates 3211, thuscausing'the stack of short sheets to rock or bounce rapidly as feederbar assembly 30a rapidly reciprocates beneath stack 40.

In the present invention, backstop assembly 20, as shown in FIG. 1,comprises backstop support 21 movably mounted in grooves provided withinfeeding surface 12 in the conventional manner. Generally there are twobackstop supports 21 mounted in feeding surface 12. A channel orbackstop support bar 24 is provided laterally above feeding surface 12connecting both backstop supports 21 in a ganged assembly and providinga backstop support unit movably mounted on feeding surface 12. Fixedlymounted on backstop support bar 24 are wedge supports 25 arranged atlaterally spaced intervals along backstop support bar 24. Backstops 22are slidably mounted on wedge supports 25 by bolts 26 and 26a and slot28, as shown in FIG. 4, thus permitting backstops 22 to be moved from anupper position to a lower position as shown in the drawing. For example,to move backstop 22 from the upper position to the lower position, bolt26 must be loosened and bolt 26a must be removed. Holes are provided inwedge 25 to accommodate bolts 26 and 26a. The holes are spaced apart ata distance corresponding substantially to the length of slot 28.Therefore, backstop 22 may be moved toward gate 50 traversing the lengthof slot 28. Bolt 26a is then replaced and both bolts 26 and 2612, now atopposite ends of slot 28, are tightened to secure backstop 22 in thelower position as shown in FIG. 1.

Backstops 22 are moved to the upper position when feeding long sheets,as shown in FIG. 1, thus enabling the conventional spring feeder barassembly 30a to be used. Backstop assembly 20 may be used successfullywith continuous chain feeders or suction feeders but the feeder barassembly 30a is believed to be the most efficient means of feeding longsheets. Furthermore, since trailing edge 43 of bottom sheet 46 rests onledge support 23 when in the upper position and leading edge 45 rests onwarped sheet deflector bar 60, there is adequate room between feedingsurface 12 and the underside of stack 40 to permit feeder bar assembly30a to reciprocate. In addition, the weight of the stack of long sheetsis sufficient to substantially deflect spring feeder plate 32a. Theresult is the efficient feeding of long sheets from the underside ofstack 40 without rocking or bouncing the stack.

When short sheets are fed, backstop assembly 20 is moved forward toaccommodate the appropriate sheet length. As this is done, the angle ofincline of stack 40, with respect to feeding surface 12 becomes greateras backstop assembly 20 is moved toward gate 50. Backstops 22 are movedto the lower position, see FIG. 1, to reduce the angle of inclinethereby maintaining stack 40 substantially horizontal. With the bottomof stack 40 closer to feeding surface 12, and since the stack of shortsheets weighs less than a stack of long sheets, the use of conventionalfeeder bar assembly 300 having stiff spring feeder plates 32a may exerta substantial upward force on the underside of stack 40, thus causingrocking of the stack as assembly 30a reciprocates in the now reducedarea between stack 40 and feeding surface 12.

However, this problem is overcome by the use of the novel low-profilefeeder bar assembly 30 of this invention as shown in FIGS. 3 and 4.Feeder bar assembly 30 comprises lowprofile feeder bar 31 having taperedleading edge 35, tapered trailing edge 36 and flat spring feeder plates32 spaced laterally along bar 31 and secured to leading edge 35 byscrews 33. At the trailing edge of spring feeder plates 32 is lipportion 34 provided to engage the trailing edge of a sheet and feed thesheet through opening 52 to the adjacent processing machinery. Springfeeder plates 32 of the present invention are more highly resilient orflexible than prior art spring feeder plates 32a and therefore exertless upward force on the bottom of stack 40 and are also lower in heightthan the conventional plates as illustrated by comparison in FIGS. 2 and3. Therefore, spring feeder plates 32 of the present invention reduce oreliminate the rocking up and down of stack 40 as feeder bar assembly 30rapidly reciprocates back and forth beneath stack 40 but still retainsthe desirable feeding characteristics of a spring feeder assembly.Feeder bar assembly 30 reciprocates above feeding surface 12 in asimilar manner to that used in the conventional feeding apparatuspreviously described.

The wedge mounted backstops 22, in addition to being movable from anupper position to a lower position, are movable toward or away from gate50 with respect to support 21. This distance, with respect to support21, is shown in FIG. 1 and designated DL. When short sheets are beingfed, the distance between support 21 and deflector 60 may approach alength substantially equivalent to the length of the stroke of thefeeder bar 31. In this case, the stroke of feeder bar 31 may requireadditional clearance to reciprocate unobstructed between deflector 60and support 21. The additional clearance required is provided by theoffset distance DL.

Spring feeder plates 32 are substantially flat. On the other hand,conventional spring feeder plates 32a FIG. 2 have a bend conforming theplate to fit over the substantially rectangular shape of conventionalfeeder bar 31a. Conventional spring feeder plates 32a require a secondbend 29 to incline the feeder plate upwards toward the bottom of stack40. Substantially flat feeder plates 32, when secured to the leadingedge of feeder bar 31 incline upwards toward the underside of the stack,as best shown in FIG. 3. The low profile of feeder bar 31 and the morehighly resilient, that is, more flexible spring feeder plates 32 operateefficiently within the reduced area between stack 40 and feeding surface12 so as to feed short and straight or warped sheets to the adjacentprocessing machinery.

It has been found that the low-profile feeder bar assembly 30 operatesefficiently for feeding sheets up to a length of about 20 to 25 incheslong in conventional sheet feeding machines, it being understood thatthis range varies a little depending on the size of the machine and thetype of board being used. However, in each operation the operator candetermine at which point it is preferable to change feeder bars. Atsheet lengths greater than this the conventional feeder bar assembly 30awas found to be more efficient.

In operation, a stack of long sheets 40 rests on ledge 23 and warpedsheet deflector bar 60 between backstop 22 and gate 50. Backstop 22 isin the upper or first position above feeding surface 12 and at adistance from gate 50 corresponding appropriately to the sheet length.

Conventional feeder bar assembly 30a reciprocates between stack 40 andfeeding surface 12 so that spring feeder plates 32a exert an upwardlydirected force on the underside of stack 40. Lip portion 34a engagestrailing edge 43 of bottom sheet 46 at the end of the backstroke. Asfeeder bar assembly 30a moves forward toward gate 50, bottom sheet 46 isadvanced through opening 52. Before the forward stroke of feeder barassembly 30a is completed, sheet 46 is engaged by adjacent processingmachinery and withdrawn completely from the underside of stack 40.Feeder bar assembly 3011 continues to reciprocate and feed thesubsequent bottom sheets from beneath stack 40.

When short sheets are to be fed, feeder bar assembly 30a is replaced bylow-profile feeder bar assembly 30, and appropriate adjustments are madefor feeding the short sheets from the bottom of stack 40. Backstop 22 isadjusted along wedge support to its lower or second position, andbackstop assembly 20 is positioned with respect to gate 50,corresponding to the length of the short sheet. Low-profile feeder barassembly reciprocates as before, sequentially feeding the bottom sheetsof stack 40 in a smooth and efficient manner.

The foregoing has described a novel sheet feeding apparatus for feedinglong and short sheets from the bottom of a stack without substantiallyrocking said stack and for effectively feeding warped sheets to theadjacent processing machinery.

Having thus described the invention in its best embodiment and mode ofoperation, that which is desired to be claimed by Letters Patent is:

l. Feeding apparatus for selectively feeding long and short sheets frombeneath a stack of sheets and along a path of travel through a meteringmeans, comprising:

a feeding surface for supporting the leading edge of said stack adjacentsaid metering means;

backstop means on said feeding surface for supporting a trailing edge ofsaid stack above said surface and being adjustable longitudinally fromsaid metering means along said path for supporting sheets of varyinglength;

said backstop means selectively adjustable between a first elevatedposition above said feeding surface and a second elevated position lowerthan said first position for supporting the trailing edge of a stack oflong sheets above said feeding surface at said first position and forsupporting the trailing edge of a stack of short sheets above saidfeeding surface at said second position; and

mutually exclusive first and second feeding means selectively mountableto a slide means in said feeding surface for reciprocation thereby,

said first feeding means reciprocable along said path for sequentiallyadvancing successive bottom sheets from beneath a stack of long sheetsthrough said metering means when said backstop means is in said firstposition, and

said second feeding means reciprocable along said path for sequentiallyadvancing successive bottom sheets from beneath a stack of short sheetsthrough said metering means when said backstop means is in said secondposition.

2. The feeding apparatus of claim 1, wherein said first feeding meansincludes a laterally extending feeder bar having spring feeders spacedat intervals therealong, said feeders having a sheet engaging surface ofsufficient height to engage the trailing edge of the bottom sheet of astack of long sheets when said backstop means is in said first position.

3. The feeding apparatus of claim 2, wherein the height of said feedersis sufficient to engage the trailing edge of a sheet whose length is inexcess of 25 inches when said backstop means is in said first position.

4. The feeding apparatus of claim 1, wherein said second feeding meansincludes a laterally extending feeder bar having spring feeders spacedat intervals therealong, said feeders having a sheet engaging surface ofsufficient height to engage the trailing edge of the bottom sheet of astack of short sheets when said backstop means is in said secondposition.

5. The feeding apparatus of claim 4, wherein the height of said feedersis sufiicient to engage the trailing edge of a sheet whose length isless than 25 inches when said backstop means is in said second position.

6. Feeding apparatus for selectively feeding long and short sheets frombeneath a stack and along a path of travel through a metering means,comprising:

a feeding surface for supporting the leading edge of said stack adjacentsaid metering means;

backstopmeans on said feeding surface for supporting the trailing edgeof said stack above said feeding surface, said backstop means including:

a laterally extending backstop bar positionable along said feedingsurface at a distance from said metering means corresponding to thelength of sheets to be fed; wedge supports spaced at intervals alongsaid backstop bar each including a top surface inclined toward saidfeeding surface in the direction of said metering means; and

backstops having inclined bottom surfaces corresponding to said topsurfaces slidably secured to said wedge supports andhaving supportledges for supporting the trailing edge of said stack above said feedingsurface at a distance corresponding to the position at which saidbackstops are secured along said inclined top surfaces; and

mutually exclusive first and second feeding means selectively mountableto a slide means in said feeding surface for reciprocation thereby,

said first feeding means reciprocable along said path of travel forsequentially advancing successive bottom sheets from beneath a stack oflong sheets when said backstops are secured at substantially theirmaximum height along said inclined top surfaces, said first feedingmeans including:

a laterally extending feeder bar including spring feeders secured atintervals therealong, said feeders including a sheet engaging surfacespaced above said feeding surface a distance sufficient to engage thetrailing edge of the bottom sheet of said stack of long sheets; and

said second feeding means reciprocable along said path of travel forsequentially advancing successive bottom sheets from beneath a stack ofshort sheets when said backstops are secured at substantially theirminimum height along said inclined top surfaces, said second feedingmeans including:

a laterally extending feeder bar including spring feeders secured atintervals therealong, said feeders including a sheet engaging surfacespaced above said feeding surface a distance sufficient to engage thetrailing edge of the bottom sheet of said stack of short sheets.

7. Feeding apparatus for selectively feeding long and short sheets frombeneath a stack of sheets and along a path of travel through a meteringmeans, comprising:

a feeding surface for supporting the leading edge of said stack adjacentsaid metering means;

backstop means on said feeding surface for supporting a trailing edge ofsaid stack above said surface and being adjustable longitudinally fromsaid metering means along said path for supporting sheets of varyinglength;

said backstop means selectively adjustable between a first elevatedposition above said feeding surface and a second elevated position lowerthan said first position for supporting the trailing edge of a stack oflong sheets above said feeding surface at said first position and forsupporting the trailing edge of a stack of short sheets above saidfeeding surface at said second position;

mutually exclusive first and second feeding means selectively mountableto a slide means in said feeding surface for reciprocation thereby.

said first feeding means reciprocable along said path for sequentiallyadvancing successive bottom sheets from beneath a stack of long sheetsthrough said metering means when said backstop means is in said firstposition, and said second feeding means reciprocable along said path forsequentially advancing successive bottom sheets from beneath a stack ofshort sheets through said metering means when said backstop means is insaid second position, said backstop means including:

a backstop support bar on said feeding surface extending along the widthof said stack and adjustable longitudinally from said metering means adistance corresponding substantially to the length of sheets beingadvanced;

wedge supports spaced at intervals along said support bar and includingtop surfaces inclined toward said feeding surface in the direction ofsaid metering means; and

backstops having inclined bottom surfaces corresponding to said inclinedtop surfaces and selectively secured thereto at said first or saidsecond position,

said backstops further including ledge supports for supporting thetrailing edge of said stack at a height substantially corresponding toeither said first or second positions.

i t i i i

1. Feeding apparatus for selectively feeding long and short sheets frombeneath a stack of sheets and along a path of travel through a meteringmeans, comprising: a feeding surface for supporting the leading edge ofsaid stack adjacent said metering means; backstop means on said feedingsurface for supporting a Trailing edge of said stack above said surfaceand being adjustable longitudinally from said metering means along saidpath for supporting sheets of varying length; said backstop meansselectively adjustable between a first elevated position above saidfeeding surface and a second elevated position lower than said firstposition for supporting the trailing edge of a stack of long sheetsabove said feeding surface at said first position and for supporting thetrailing edge of a stack of short sheets above said feeding surface atsaid second position; and mutually exclusive first and second feedingmeans selectively mountable to a slide means in said feeding surface forreciprocation thereby, said first feeding means reciprocable along saidpath for sequentially advancing successive bottom sheets from beneath astack of long sheets through said metering means when said backstopmeans is in said first position, and said second feeding meansreciprocable along said path for sequentially advancing successivebottom sheets from beneath a stack of short sheets through said meteringmeans when said backstop means is in said second position.
 2. Thefeeding apparatus of claim 1, wherein said first feeding means includesa laterally extending feeder bar having spring feeders spaced atintervals therealong, said feeders having a sheet engaging surface ofsufficient height to engage the trailing edge of the bottom sheet of astack of long sheets when said backstop means is in said first position.3. The feeding apparatus of claim 2, wherein the height of said feedersis sufficient to engage the trailing edge of a sheet whose length is inexcess of 25 inches when said backstop means is in said first position.4. The feeding apparatus of claim 1, wherein said second feeding meansincludes a laterally extending feeder bar having spring feeders spacedat intervals therealong, said feeders having a sheet engaging surface ofsufficient height to engage the trailing edge of the bottom sheet of astack of short sheets when said backstop means is in said secondposition.
 5. The feeding apparatus of claim 4, wherein the height ofsaid feeders is sufficient to engage the trailing edge of a sheet whoselength is less than 25 inches when said backstop means is in said secondposition.
 6. Feeding apparatus for selectively feeding long and shortsheets from beneath a stack and along a path of travel through ametering means, comprising: a feeding surface for supporting the leadingedge of said stack adjacent said metering means; backstop means on saidfeeding surface for supporting the trailing edge of said stack abovesaid feeding surface, said backstop means including: a laterallyextending backstop bar positionable along said feeding surface at adistance from said metering means corresponding to the length of sheetsto be fed; wedge supports spaced at intervals along said backstop bareach including a top surface inclined toward said feeding surface in thedirection of said metering means; and backstops having inclined bottomsurfaces corresponding to said top surfaces slidably secured to saidwedge supports and having support ledges for supporting the trailingedge of said stack above said feeding surface at a distancecorresponding to the position at which said backstops are secured alongsaid inclined top surfaces; and mutually exclusive first and secondfeeding means selectively mountable to a slide means in said feedingsurface for reciprocation thereby, said first feeding means reciprocablealong said path of travel for sequentially advancing successive bottomsheets from beneath a stack of long sheets when said backstops aresecured at substantially their maximum height along said inclined topsurfaces, said first feeding means including: a laterally extendingfeeder bar including spring feeders secured at intervals therealong,said feeders including a sheet engaging surface spaced above saidfeeding surface a Distance sufficient to engage the trailing edge of thebottom sheet of said stack of long sheets; and said second feeding meansreciprocable along said path of travel for sequentially advancingsuccessive bottom sheets from beneath a stack of short sheets when saidbackstops are secured at substantially their minimum height along saidinclined top surfaces, said second feeding means including: a laterallyextending feeder bar including spring feeders secured at intervalstherealong, said feeders including a sheet engaging surface spaced abovesaid feeding surface a distance sufficient to engage the trailing edgeof the bottom sheet of said stack of short sheets.
 7. Feeding apparatusfor selectively feeding long and short sheets from beneath a stack ofsheets and along a path of travel through a metering means, comprising:a feeding surface for supporting the leading edge of said stack adjacentsaid metering means; backstop means on said feeding surface forsupporting a trailing edge of said stack above said surface and beingadjustable longitudinally from said metering means along said path forsupporting sheets of varying length; said backstop means selectivelyadjustable between a first elevated position above said feeding surfaceand a second elevated position lower than said first position forsupporting the trailing edge of a stack of long sheets above saidfeeding surface at said first position and for supporting the trailingedge of a stack of short sheets above said feeding surface at saidsecond position; mutually exclusive first and second feeding meansselectively mountable to a slide means in said feeding surface forreciprocation thereby, said first feeding means reciprocable along saidpath for sequentially advancing successive bottom sheets from beneath astack of long sheets through said metering means when said backstopmeans is in said first position, and said second feeding meansreciprocable along said path for sequentially advancing successivebottom sheets from beneath a stack of short sheets through said meteringmeans when said backstop means is in said second position, said backstopmeans including: a backstop support bar on said feeding surfaceextending along the width of said stack and adjustable longitudinallyfrom said metering means a distance corresponding substantially to thelength of sheets being advanced; wedge supports spaced at intervalsalong said support bar and including top surfaces inclined toward saidfeeding surface in the direction of said metering means; and backstopshaving inclined bottom surfaces corresponding to said inclined topsurfaces and selectively secured thereto at said first or said secondposition, said backstops further including ledge supports for supportingthe trailing edge of said stack at a height substantially correspondingto either said first or second positions.